Blade of a turbomachine made of different materials and method for the production thereof

ABSTRACT

The present invention relates to a blade for a turbomachine, in particular for an aircraft engine, which comprises a blade root ( 2 ) for arranging the blade ( 1 ) in the turbomachine and a main blade part ( 3 ) for interaction with a fluid flowing through the turbomachine, the blade root and the main blade part being formed from different materials and the main blade part being formed from a metal-intermetallic composite material. The metal matrix, in which intermetallic phases are incorporated for forming the metal-intermetallic composite material, is formed by a molybdenum alloy. The invention also relates to a corresponding method for producing such a blade.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 of European Patent Application No. 15159308.4, filed Mar. 17, 2015 and of European Patent Application No. 15188446.7, filed Oct. 6, 2015, the entire disclosures of which are expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a blade for a turbomachine, in particular for an aircraft engine, and also to a method for producing such a blade.

2. Discussion of Background Information

In turbomachines, such as static gas turbines or aircraft engines, the components used have to satisfy stringent requirements in various property ranges depending on the field of use, for example the lowest possible weight together with high strength and adequate ductility, creep strength, high-temperature stability, vibration stability, etc.

In particular, there are also individual components of turbomachines, for example blades, which have to satisfy different and sometimes opposing requirements with respect to the properties. It is therefore advantageous, for example in the case of rotor blades of high-speed low-pressure turbines, if the blade root, with which the blade is received in a turbine disk, has a high tensile strength and a high elongation potential, whereas the main blade part, which interacts with the fluid flowing through the turbomachine, should primarily have a high oxidation resistance and creep strength.

In order to make it possible to satisfy these different requirements in a targeted manner, it is already known from the prior art to form the main blade part and the blade root from different materials. By way of example, European patent application EP 1 743 729 A2, the entire disclosure of which is incorporated by reference herein, describes producing a blade for a turbomachine from niobium-silicide compounds, in which the niobium-silicide alloy is different in certain regions of the turbine blade compared to other regions of the turbine blade.

However, the niobium-silicide alloys described in EP 1 743 729 A2 are unable to satisfy the requirements of modern turbomachines and in particular of high-speed low-pressure turbines, since they do not satisfy the required structural-mechanical properties with respect to creep strength, tensile strength and elongation potential, and also do not satisfy the requirements with respect to oxidation resistance.

In view of the foregoing, it would be advantageous to have available a blade for a turbomachine and in particular for a high-speed low-pressure turbine of an aircraft engine which satisfies the corresponding requirements with respect to tensile strength, elongation, creep strength and oxidation resistance. In this respect, the blade should as far as possible be easy to produce and be reliable during operation.

SUMMARY OF THE INVENTION

The present invention provides a blade for a turbomachine, in particular for an aircraft engine. The blade comprises a blade root for arranging the blade in the turbomachine and a main blade part for interaction with a fluid flowing through the turbomachine. The blade root and the main blade part are formed from different materials, the main blade part being formed from a metal-intermetallic composite (MIC) material wherein the metal matrix, in which intermetallic phases are incorporated for forming the MIC material, is formed by a molybdenum alloy.

In one aspect of the blade of the present invention, the blade root may be formed from a MIC material in which the metal matrix, in which intermetallic phases are incorporated for forming the MIC material, is formed from a molybdenum alloy, the proportion of intermetallic phases being lower in the MIC material compared to the material of the main blade part. Further, the intermetallic phases may be or comprise silicides. Also, the MIC material of the blade root may have a silicide proportion of lower than 50% by volume.

In another aspect of the blade, the blade root may be formed from an alloy which is selected from nickel alloys, Mo alloys, and Co alloys.

In yet another aspect, the intermetallic phases of the MIC material of the main blade part may be or comprise silicides. For example, the silicides may comprise one or both of (Mo, Ti)₅Si₃ and (Mo, Ti)₅SiB₂ and/or may comprise one or more of Mo₅Si₃ Mo₅SiB₂ or Mo₃Si. Also by way of example, the MIC material of the main blade part may comprise a silicide proportion of higher than or equal to 50% by volume.

In a still further aspect of the blade, in addition to molybdenum and silicon, the molybdenum alloy forming the metal matrix of the MIC material of the main blade part and/or the molybdenum alloy forming the metal matrix of the MIC material of the blade root may comprise one or more of boron, titanium, zirconium, niobium, tungsten, iron, yttrium. For example, the molybdenum alloy may comprise from 9 at % to 15 at. % silicon, from 5 at % to 12 at. % boron, and from 18 at % to 32 at. % titanium.

In another aspect of the blade of the present invention, the transition from the material of the blade root to the material of the main blade part may be graded with a continuously running transition, or may be stepped with one or more sudden changes.

The present invention also provides a method for producing a blade for a turbomachine, in particular a blade as set forth above (including the various aspects thereof. The method comprises providing a first material for a blade root and a second material for a main blade part, the second material being different from the first material. The first material and the second material are provided in the form of a powder or a powder mixture or as solid bodies, and the blade is produced by (i) joining at least two solid bodies or (ii) joining a solid body to a powder or a powder mixture or (iii) joining at least two different powders or powder mixtures.

In one aspect of the method, the solid bodies may be joined by at least one of welding, friction welding, diffusion welding, laser beam welding, electron beam welding and inductive pressure welding.

In another aspect of the method, a powder or a powder mixture may be joined to a solid body by a generative production method for the layered application of powder particles or by providing the powder particles in a mold or capsule on the solid body and by compaction and connection of the powder particles to one another and to the solid body by at least one of hot isostatic pressing, cold isostatic pressing, hot pressing, sintering, pressure sintering and reaction sintering.

In yet another aspect, at least two different powders or powder mixtures may be joined by a generative production method for the layered connection of powder particles or by providing the powder particles in a mold or capsule and by compaction and connection of the powder particles to one another by at least one of hot isostatic pressing, cold isostatic pressing, hot pressing, sintering, pressure sintering and reaction sintering.

The invention proposes a blade for a turbomachine and in particular an aircraft engine, in which the blade root for arranging the blade in the turbomachine and the main blade part for interaction with a fluid flowing through the turbomachine are formed from different materials. In particular, the main blade part is to be formed from a metal-intermetallic composite (MIC) material, in which the metal matrix, in which the intermetallic phases of the metal-intermetallic composite material are incorporated, is formed from a molybdenum alloy. It has been found that molybdenum alloys reinforced by intermetallic phases in particular satisfy the property profile for a main blade part of a corresponding blade and at the same time make it possible to easily provide an integrally connected blade root, which can likewise satisfy the requirements with respect to a high tensile strength and high ductility. Specifically, this can be achieved in a simple manner by virtue of the fact that a metal-intermetallic composite material comparable to that used for the main blade part is also used for the blade root, with merely the proportion of the intermetallic phases in the metal-intermetallic composite material being reduced compared with the material of the main blade part, in order to thereby increase the tensile strength and the elongation potential. The use of a similar material likewise comprising a molybdenum alloy as the metal matrix ensures a particularly good and simple bond of the blade root to the main blade part. In addition, it is possible, however, to also form the blade root from other molybdenum alloys without the incorporation of intermetallic phases or through nickel alloys or cobalt alloys and in particular corresponding superalloys of these alloys. Both Mo alloys and Ni alloys and Co alloys afford a good possibility of connection to Mo-based metallic-intermetallic composite materials, and provide suitable mechanical properties for the formation of a blade root.

The intermetallic phases that can be incorporated in the molybdenum alloy of the main blade part and/or of the blade root can preferably be silicides, such as Mo₅Si₃ and/or Mo₅SiB₂ and/or Mo₃Si.

In addition to molybdenum and silicon, the molybdenum alloy that can form the metal matrix for the metal-intermetallic composite material of the main blade part and also of the blade root can in particular also comprise boron, titanium, zirconium, niobium, tungsten, iron and/or yttrium.

An Mo-based metal-intermetallic composite material that can be used for the present invention is described in German patent application DE 102015214730.4, the entire disclosure of which is incorporated by reference herein.

When using a silicide-reinforced metal-intermetallic composite material and in particular a silicide-reinforced molybdenum alloy for the main blade part and/or the blade root, the silicide proportion of the material in the main blade part can amount to 50% by volume and more, while the silicide proportion in the blade root can be chosen to be lower than 50% by volume.

Instead of an abrupt transition from the material of the blade root to the main blade part, it is also possible for a continuous, graded transition to be set, such that the material changes gradually in a transition region from the blade root to the main blade part. In addition, provision can also be made of a plurality of small step transitions in the transition region between the blade root and the main blade part, so as not to create a continuous transition from the material of the blade root to the main blade part, but to keep the changes in the chemical composition at the respective steps small. In addition, provision can also be made of any desired third material between the blade root and the main blade part, where in turn the transitions from the material of the blade root to the third material and from the third material to the substance of the main blade part can be provided in continuously graded form or in one or more steps. A third material can be provided, for example, for a shroud between the main blade part and the blade root.

To produce a corresponding blade for a turbomachine comprising a different material in the blade root and in the main blade part, the first material for the blade root on the one hand and the second material for the main blade part on the other hand can be provided in the form of powders or powder mixtures or as solid bodies, it then being possible for the blade to be produced by joining at least two solid bodies or by joining a solid body to a powder or a powder mixture or by joining at least two different powders or powder mixtures.

If provision is made of at least two solid bodies made of different materials which are accordingly intended to form the regions of the blade root and of the main blade part, the solid bodies can be joined by a welding method, such as for example friction welding, diffusion welding, laser beam welding, electron beam welding or inductive pressure welding.

When joining powder or a powder mixture to a solid body or when joining at least two different powders or powder mixtures, it is possible to use generative production methods for the layered deposition of powder particles, such as for example selective laser beam melting, selective laser beam sintering, selective electron beam melting, selective electron beam sintering, laser build-up welding and the like. In these methods, a further layer of powder is built up either on the already previously provided solid body or a layer already previously produced from a powder by the fusion or sintering of the powder particles with one another and with the underlying solid body, to form a body, with a change in the chemical composition of the powders or powder mixtures compared to the underlying solid body or the already joined powder making it possible to produce a transition from one material, as is to be provided in the blade root, to a different material, as is to be provided in the main blade part.

In addition, powder particles can be connected to one another or to a corresponding solid body in such a way as to provide a mold or capsule into which the powder can be introduced, it being possible for a corresponding body for producing a blade comprising two different materials to be produced by compaction and connection of the powder particles by hot isostatic pressing, cold isostatic pressing, hot pressing, sintering, pressure sintering and/or reaction sintering.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings show, in a purely schematic manner, in

FIG. 1 a perspective illustration of a blade for an aircraft engine,

FIG. 2 a flow chart for a first embodiment of a method for producing a blade,

FIG. 3 a flow chart for a second embodiment of a method for producing a blade,

FIG. 4 a flow chart for a third embodiment of a method for producing a blade, and

FIG. 5 a flow chart of a fourth embodiment for a method for producing a blade.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description in combination with the drawings making apparent to those of skill in the art how the several forms of the present invention may be embodied in practice.

FIG. 1 shows a perspective illustration of a blade 1, as can be used for example as a rotor blade in the front stages of high-speed low-pressure turbines.

The blade 1 has a blade root 2, by way of which it can be inserted into a turbine disk. In addition, the blade 1 comprises a main blade part 3, which is subjected to the fluid flowing past and contributes to the driving of the turbine blade.

The turbine blade 1 has an inner shroud 4 between the blade root 2 and the main blade part 3. According to the invention, the main blade part 3 is formed from a different material to the blade root 2, in order to satisfy the different requirements in respect of the main blade part 3 and the blade root 2. The inner shroud 4 can be formed either from the material of the main blade part 3 or the material of the blade root 2 or from a third material which differs from the materials of the blade root 2 and of the main blade part 3.

According to the invention, the blade root 2 can be formed from suitable high-temperature alloys, such as molybdenum alloys, nickel alloys, cobalt alloys and in particular nickel-based superalloys or cobalt-based superalloys. In addition, the blade root 2 can be formed from a metallic-intermetallic composite material, in which the metal matrix can be formed in particular from a molybdenum alloy. As intermetallic phases, the corresponding metallic-intermetallic composite material can comprise silicides.

In addition to the main constituent, molybdenum, which thus makes up the greatest proportion of the alloy, the molybdenum alloy can comprise silicon, boron, titanium, iron, yttrium, zirconium, niobium and tungsten. By way of example, the alloy can comprise from 9 at % to 15 at. % silicon, from 5 at % to 12 at. % boron, from 18 at % to 32 at. % titanium, remainder molybdenum, it being possible for the further alloying elements mentioned to also be present in the alloy in smaller proportions. The silicide phases can be formed by (Mo, Ti)₅Si₃ and/or (Mo, Ti)₅SiB₂, where in the respective silicides molybdenum can be replaced at least partially by titanium, and vice versa.

The molybdenum alloy can comprise from 15% to 35% by volume (Mo, Ti)₅Si₃ and from 20% to 40% by volume (Mo, Ti)₅SiB₂, the total proportion of the silicide phases preferably being kept below 50% by volume for the material of the blade root 2.

A similar material can be used for the main blade part 3, with the corresponding amounts for the chemical composition being identical. The composition and the heat treatment are chosen, however, in such a way that the silicide proportion is ≧50% by volume, in order to provide the main blade part with a higher creep strength and better oxidation resistance, whereas the blade root comprising the comparable silicide-reinforced molybdenum alloy but having a silicide proportion of <50% by volume has a higher tensile strength and a higher elongation potential.

The turbine blade 1 as shown in FIG. 1 can be produced by various production methods, with corresponding flow charts being shown in FIGS. 2 to 5.

In the case of the production as per the embodiment shown in FIG. 2, provision is firstly made of powder particles, which can be used to produce the above-described molybdenum alloys with silicide reinforcement (method step 10). Two different powder mixtures which can be used to produce the two different materials for the blade root 2 and the main blade part 3 are mixed (step 11) from the powder particles, which can be formed for example as pure elemental particles, alloy particles, coated particles and/or particles consisting of intermetallic phases and/or chemical compounds.

In method steps 12, 13, 14 and 15, the two different powder mixtures are processed separately from one another to form separate solid bodies, of which one will form the blade root 2 and the other will form the main blade part 3.

In the following method step, method step 16, the two solid bodies are connected to one another, it being possible to use various welding methods, such as friction welding, diffusion welding, inductive pressure welding, electron beam welding or laser welding.

After the joining of the solid bodies made of different materials, such as a silicide-reinforced molybdenum alloy with a high silicide proportion and a silicide-reinforced molybdenum alloy with a low silicide proportion, the joined body can be reworked to form a turbine blade 1, for example by machining for shaping, by heat treatment for setting the desired microstructure and also by surface treatment and/or coating to form the desired surface (method step 17).

FIG. 3 shows a further variant of a production method, in which, in step 20, provision is already made of a solid body made of one of the desired materials. By way of example, the solid body could be produced from one of the high-temperature alloys that can be used for the blade root, such as for example a conventional molybdenum alloy or a nickel-based superalloy or a cobalt superalloy, by a powder metallurgy process or by casting and possibly subsequent forging. In step 22, a solid body produced in this way can be provided with a capsule, into which a powder mixture produced in step 21 can be introduced. The powder mixture produced in step 21 is produced in such a way that a material for the main blade part 3 can be produced therewith. Correspondingly, the capsule which is fastened to the solid body in step 22 is also formed in such a way that the powder mixture introduced from step 21 is shaped to give a semifinished part in step 23 by the subsequent hot isostatic pressing (HIP), in which semifinished part the powder mixture received in the capsule forms the material for the main blade part 3. This produces a semifinished part in which a region for the blade root is formed with a first material and a further region for the main blade part is formed with a second material which differs from the first material. In step 24, the semifinished part thus produced can be correspondingly reworked, with various reworking options again being available, such as for example shaping by machining, heat treatment, surface treatment and/or coating.

FIG. 4 shows a further embodiment of a production method, in which, in method step 30, provision is made of two different powder mixtures for producing the different materials for the main blade part 3 and the blade root 2. The two different powder mixtures are introduced in succession into an elastic mold in two layers (method step 31), in order subsequently firstly to be subjected to cold isostatic pressing and then joined to form a semifinished product during reaction sintering in method steps 32 and 33. The reaction sintering in method step 33 can be followed by, for compaction, hot isostatic pressing in method step 34 and thermomechanical shaping by forging in method step 35. The introduction of the powder mixtures in two different layers thus in turn produces a semifinished product having a region made of a first material and a region made of a second material, such that a blade 1 comprising a blade root 2 made of a first material and a main blade part 3 made of a second material can be formed correspondingly with the different regions. The finishing can be effected in method step 36 again by heat treatment, machining, surface treatment and/or coating.

FIG. 5 shows a further embodiment of a method for producing a turbine blade as is shown in FIG. 1, wherein in this design variant provision is again made of two different powder mixtures for producing the different materials for the blade root 2 and the main blade part 3 (method step 40). The two different powder mixtures are used for the layered production of the blade by a generative method, wherein firstly the first powder mixture is used to produce the first material in the blade root 2 and then the second powder mixture is used to produce the main blade part 3 and the second material provided there. If the blade is not to be built up from the blade root toward the main blade part, but rather in another direction, it is of course also possible for the different powder mixtures to be used in a locally separate manner, instead of a chronologically separate use of the different powder mixtures, during the generative production method, in order to form separate regions from the two different materials.

Selective laser beam melting, selective laser beam sintering, electron beam melting or electron beam sintering and also laser beam or electron beam build-up welding can be used, for example, as the generative production methods.

In respect of the production methods described, it has merely been described to date that two separate regions comprising different materials are produced for forming the blade root 2 and the main blade part 3. However, it goes without saying that it is also possible to vary the materials within the blade root 2 and/or the main blade part 3 in order in particular to realize a graded, continuous transition from the blade root 2 to the main blade part 3. Correspondingly, the production methods presented can be accordingly adapted in order to produce a continuous variation of the material. In the case of those methods in which powders or powder mixtures are used for producing a component region, this can easily be achieved by a continuous variation of the powder composition.

While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

The entire disclosure of co-assigned patent application Ser. No. 15/066,186, filed Mar. 10, 2016, is incorporated by reference herein.

DEFINITIONS

Elemental particles are understood to mean powder particles which are formed essentially from a single chemical element, whereas alloy particles are formed from an alloy.

Superalloys are understood to mean alloys having an operating temperature which lies in a temperature range above half the melting temperature of the alloy, in particular above 75% of the melting temperature of the alloy and preferably above 90% of the melting temperature of the alloy.

LIST OF REFERENCE NUMERALS

-   1 Turbine blade -   2 Blade root -   3 Main blade part -   4 Inner shroud -   10 to 42 Method steps 

What is claimed is:
 1. A blade for a turbomachine, wherein the blade comprises a blade root for arranging the blade in the turbomachine and a main blade part for interaction with a fluid flowing through the turbomachine, the blade root and the main blade part being formed from different materials and the main blade part being formed from a metal-intermetallic composite (MIC) material wherein a metal matrix, in which intermetallic phases are incorporated for forming the MIC material, is formed by a molybdenum alloy.
 2. The blade of claim 1, wherein the blade root is formed from a MIC material in which the metal matrix, in which intermetallic phases are incorporated for forming the MIC material, is formed from a molybdenum alloy, a proportion of intermetallic phases being lower in the MIC material compared to the MIC material of the main blade part.
 3. The blade of claim 1, wherein the blade root is formed from an alloy which is selected from nickel alloys, Mo alloys, and Co alloys.
 4. The blade of claim 1, wherein the intermetallic phases are or comprise silicides.
 5. The blade of claim 4, wherein the silicides comprise one or both of (Mo, Ti)₅Si₃ and (Mo, Ti)₅SiB₂.
 6. The blade of claim 4, wherein the silicides comprise one or more of Mo₅Si₃ Mo₅SiB₂ and Mo₃Si.
 7. The blade of claim 2, wherein the intermetallic phases are or comprise silicides.
 8. The blade of claim 1, wherein the MIC material of the main blade part comprises a silicide proportion of higher than or equal to 50% by volume.
 9. The blade of claim 2, wherein the MIC material of the blade root has a silicide proportion of lower than 50% by volume.
 10. The blade of claim 1, wherein in addition to molybdenum and silicon, the molybdenum alloy forming the metal matrix of the MIC material of the main blade part comprises one or more of boron, titanium, zirconium, niobium, tungsten, iron, yttrium.
 11. The blade of claim 10, wherein the molybdenum alloy comprises from 9 at % to 15 at. % silicon, from 5 at % to 12 at. % boron, and from 18 at % to 32 at. % titanium.
 12. The blade of claim 2, wherein in addition to molybdenum and silicon, the molybdenum alloy forming the metal matrix of the MIC material of the blade root comprises one or more of boron, titanium, zirconium, niobium, tungsten, iron, yttrium.
 13. The blade of claim 1, wherein a transition from the material of the blade root to the material of the main blade part is graded with a continuously running transition.
 14. The blade of claim 1, wherein a transition from the material of the blade root to the material of the main blade part is stepped with one or more sudden changes.
 15. A method for producing a blade for a turbomachine, wherein the method comprises providing a first material for a blade root and a second material for a main blade part, the second material being different from the first material, and wherein the first material and the second material are provided in the form of a powder or a powder mixture or as solid bodies, and the blade is produced by (i) joining at least two solid bodies or (ii) joining a solid body to a powder or a powder mixture or (iii) joining at least two different powders or powder mixtures.
 16. The method of claim 15, wherein the solid bodies are joined by at least one of welding, friction welding, diffusion welding, laser beam welding, electron beam welding and inductive pressure welding.
 17. The method as claimed in claim 15, wherein a powder or a powder mixture is joined to a solid body by a generative production method for a layered application of powder particles or by providing the powder particles in a mold or capsule on the solid body and by compaction and connection of the powder particles to one another and to the solid body by at least one of hot isostatic pressing, cold isostatic pressing, hot pressing, sintering, pressure sintering and reaction sintering.
 18. The method as claimed in claim 15, wherein at least two different powders or powder mixtures are joined by a generative production method for a layered connection of powder particles or by providing the powder particles in a mold or capsule and by compaction and connection of the powder particles to one another by at least one of hot isostatic pressing, cold isostatic pressing, hot pressing, sintering, pressure sintering and reaction sintering.
 19. An turbomachine which comprises the blade of claim
 1. 20. The turbomachine of claim 19, which is an aircraft engine. 